This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined below, after the main part of the detailed description section.
At 3GPP LTE RAN #69 plenary meeting, a new work item named NB-IoT was approved. According to the WID, NB-IoT will support the following three operation modes:                Stand-alone operation, utilizing for example the spectrum currently being used by GERAN systems as a replacement of one or more GSM carriers.        Guard-band operation, utilizing the unused resource blocks within an LTE carrier's guard-band.        In-band operation, utilizing resource blocks within a normal LTE carrier.        
The NB-IoT is expected to support up to a 20 dB coverage improvement, a massive number of low throughput devices, low delay sensitivity, ultra-low device cost, low device power consumption, and (e.g., optimized) network structure. Furthermore, NB-IoT bandwidth is only 180 kHz, corresponding to one PRB (and 12 subcarriers) in LTE.
At the 3GPP RAN1#83 meeting, it was agreed that a proposal for NB-IoT DL channel is for downlink transmission with 15 kHz subcarrier spacing for all the modes: stand-alone, guard-band, and in-band. Additionally, the working assumptions are that NB-IoT supports operation with more than one DL Tx antenna port and for operation with two DL Tx antenna ports, NB-IoT uses SFBC.
There is, however, no clear design of a control channel for the NB-IoT downlink or uplink channels.